Enter partitioning tool

Press p and make sure that new setup looks similar to the base one (from step 1.)

Press w to save settings

You are suppose to see that message:

The partition table has been altered.
Calling ioctl() to re-read partition table.
Re-reading the partition table failed.: Device or resource busy
The kernel still uses the old table. The new table will be used at the next reboot or after you run partprobe(8) or kpartx(8).